Device for bending pipes with simultaneous upsetting

ABSTRACT

Known in the art are devices for bending pipes with simultaneous upsetting wherein the pipe is bent with the aid of a turning bending head which clamps one end of the pipe to be bend; bending is effected when the pipe is fed longitudinally by power cylinders towards the bending head whose turning is retarded by another power cylinder called braking cylinder. A distinctive feature of the device according to the invention is the provision of one more power cylinder whose body is connected rigidly with the body of the braking power cylinder, the latter being linked kinematically by its movable body with the bending head while the space of the power cylinder connected with the braking cylinder communicates with an individual controllable source of pressure. An advantage of the device according to the invention lies in that there is a definite relationship at each given moment of time between the rate of longitudinal pipe feed and the turning speed of the bending head. This eliminates the nonuniformity of axial compression of the pipe being bent caused mainly by the variations in the mechanical properties of the pipe and thus ensures uniform thickness of the pipe in the bending zone and throughout the pipe.

United States Patent Somov et al.

DEVICE FOR BENDING PIPES WITH SIMULTANEOUS UPSETTING Filed: Sept. 12, 1974 Appl. No.: 505,596

U.S. Cl. 72/28; 72/310; 72/369 Int. Cl B2lb 37/06 Field of Search 72/174, 175, 166, 298,

References Cited UNITED STATES PATENTS 8/1938 Thompson 72/28 10/1957 Bower 72/23 10/1965 Hills 72/28 [451 Aug. 19, 1975 Primary ExaminerC. W. Lanham Assistant Examiner-Robert M. Rogers Attorney, Agent, or Firml-lolman & Stern [57] ABSTRACT Known in the art are devices for bending pipes with simultaneous upsetting wherein the pipe is bent with the aid of a turning bending head which clamps one end of the pipe to be bend; bending is effected when the pipe is fed longitudinally by power cylinders towards the bending head whose turning is retarded by another power cylinder called braking cylinder.

A distinctive feature of the device according to the invention is the provision of one more power cylinder whose body is connected rigidly with the body of the braking power cylinder, the latter being linked kinematically by its movable body with the bending head while the space of the power cylinder connected with the braking cylinder communicates with an individual controllable source of pressure.

An advantage of the device according to the invention lies in that there is a definite relationship at each given moment of time between the rate of longitudinal pipe feed and the turning speed of the bending head.

This eliminates the nonuniformity of axial compression of the pipe being bent caused mainly by the variations in the mechanical properties of the pipe and thus ensures uniform thickness of the pipe in the bending zone and throughout the pipe.

3 Claims, 3 Drawing Figures PATENTEDAUG-l 9l975 3, 899,908

SHEET 1 BF 2 DEVll'CE FOR BENDING PllPES WITH S1MU1LTANEOUS UPSETTHNG- At present, the devices which bend pipes with simultaneous upsetting are in predominant use, particularly while building such vital projects as pressure pipelines and heating-and-power plants.

This preference is explained by the fact that in free bending of pipes, i.e., without upsetting, the walls of the pipe are thinned out on the side subjected to tensile stresses.

As a result, the bent section of the pipe is of unequal strength, i.e., weakened at the point where it is thinner then the remaining part of the pipe.

The present invention is aimed at improving the device for bending pipes with simultaneous upsetting. Known at present are devices for bending pipes with upsetting wherein the pipes are bent with the aid of a bending templet made in the form of a power-operated disc fastened to which is the front end of the pipe to be bent. In the course of bending the pipe is moved longitudinally towards the bending templet by some kind of a drive included in the same device and acting on the rear end of the pipe.

The basic disadvantage of these devices resides in the difficulties involved in bending the pipe to radii up to 1.4 of its outside diameter due to a low strength of the bending templet and low ductility of pipe metal when cold.

Besides, these devices call for the use of highly powerful drives for bending large-diameter pipes.

Also known in the previous art are devices for hotbending of pipes with simultaneous axial compression.

Some of these devices comprise a power-operated bending head in which the front end of the pipe is installed, and a drive which acts via a pusher on'the rear end of the pipe being bent and which feeds the pipe longitudinally towards the bending head in the course of bending.

The bending head is turned and the pipe is moved longitudinally by individual drives or a common drive via a kinematic linkage which ensures turning of the bending head and longitudinal feed of the pipe at unequal preset speeds at which the pipe is axially com pressed in the course of bending (see, for example, Authors Certificate No. 163,873, C1.49h, l8, USSR),

Besides, there are similar devices wherein the bending head is not power-operated but is braked by a power cylinder whose rod is connected with the bending head body in such a way as to oppose free turning of the bending head under the action of the pipe (see, for example, the device covered by the Authors Certificate No. 183,034, Cl.49h 18, USSR).

Also known in the art are devices for hot-bending of pipes with simultaneous axial compression wherein the pipe is installed in the bed which is immovable longitudinally, while the bending head is turned by the drive along a curvilinear trajectory which is determined by the guide (see, for example, application No. 1,935,100, C1.7c 9/18, Federal Repulic of Germany).

The bendinghead contacts said guide via a pusher and a master form.

On turning of the bending head said pusher moves simultaneously the pipe in a radial direction. This ensures axial compression of the pipe in the course of bending.

A common disadvantage of all the above-described devices lies in that at any given moment of time there is no relation between the rate of the longitudinal feed of the pipe and the turning speed of the bending head. This results in nonuniform axial compression of the pipe due to variations in its longitudinal feed this being caused basically by variations in the mechanical properties of the pipe, the thickness of its walls and the heating and cooling conditions.

In turn, the nonuniformity of axial compression results in a considerable nonuniformity of the wall thickness along the length of the bent zone and, consequently, in different strength of the bent and straight zones of the pipe.

The main object of the invention is to provide a device for bending pipes with simultaneous axial compression which would ensure changes in the turning speed of the bending head to suit the changes in the rate of longitudinal feed of the pipe which is caused by variations in the mechanical properties, the wall thickness of the pipe being bent, etc.

The practical objects of the invention are to ensure uniformity of axial compression under all conditions and, consequently, the adequate equality of wall thickness and strength of the pipes, to allow bending of pipes from different materials and to any radius irrespective of the outside diameter of the pipe; to reduce the power rating of the drives, simplify and lighten the device while reatining the same operating efficiency.

Other objects and advantages of the invention will become apparent from the description that follows.

This object is accomplished by providing a device for bending pipes with simultaneous upsetting comprising a bed in which the pipe to be bent is set with a provision for being moved longitudinally by power cylinders, a bending head mounted on the bed so that it can turn in the bending plane, and another power cylinder whose movable portion is connected with the bending head and which builds up a braking moment while said head is turned in the course of bending wherein, according to the invention, it has one more power cylinder whose body is rigidly connected with the body of the braking power cylinder while its inside space communicates with an individual source of controllable pressure, the braking cylinder being connected with the bending head by its body which is its movable element.

This design makes it possible to set the braking speed of the bending head and, consequently, the degree of pipe upsetting regardless of the variations in the wall thickness and, correspondingly, of the changes in the resistance of the pipe along its length. This rules out the formation of wrinkles.

In the above-described version of the device it is highly practicable that the body of the power cylinder should be connected with the body of the bending head by a gear-and-rack transmission. This ensures better interaction between the movable body of the braking power cylinder and the bending head body.

It is likewise practicable to put the braking cylinder in communication with the power cylinders used for longitudinal feed of the pipe.

Now the invention will be described in detail by way of example with reference to the accompanying drawings in which:

FIG. 1 is a plan view of the device for bending pipes with simultaneous upsetting according to the invention.

FIG. 2 is a side view of the same device.

FIG. 3 is a diagrammatic representation of the device showing the longitudinal feed cylinders, a braking power cylinder and an auxiliary power cylinder interlocked with the braking cylinder.

The device for bending pipes with simultaneous upsetting comprises a bed 1 (FIGS. 1 and 2) which mounts a system of free-rotating rollers 2 (FIG. 1) arranged in a longitudinal row and intended to accommodate the pipe being bent; hydraulic cylinders 3 (FIGS. 1, 2 and 3) ensuring longitudinal feed of the pipe over the rollers 2 in the course of bending.

The longitudinal movement of the pipe is effected by a stop 4 (FIGS. 1 and 3) which is connected by rods 5 and cross-piece 6 (FIGs. l, 2 and 3) with the movable rods 7 of the hydraulic cylinders 3.

The stop 4 is installed on the rods 5 with a provision for moving along these rods and for being fixed in each individual position. Such a movement of the stop 4 is required for handling the pipes of various lengths.

To provide for the above-mentioned movement of the stop 4 the latter is installed on a carriage (not shown in the drawing) which is operated by a drive of its own. The mechanism for moving the stop is not described here in detail since it is a conventional part of such pipe-bending devices and is not directly concerned with the present invention.

The bed also mounts a bending head 8 installed rotatably in the pipe-bending plane. In our version of the device the turning axis of the bending head is offset from the longitudinal axis of the installation.

The bending head 8 includes a cantilever portion 9 (FIG. 3) and abushed portion 10, both being rigidly connected to each other. The cantilever portion 9 of the bending head 8 has a stop 11 on which one end of the pipe 12 is slipped (FIGS. I and 3). The bushed portion is free to turn on an axle 13 (FIGS. 1, 3) which is mounted on a slide 14 (FIG. 2), the latter being provided with a projection 15 (FIG. 2) entering a transverse slot of the bed I. The slide is moved in the slot of the bed by a drive 16 (FIG. 1).

The above-described design of the head is not imperative in realizing our invention and the head can take other reasonable forms. For example, we have devised a rational design of the bending head which is not dealt with here since we have covered it in another application.

The slide 14 also mounts a hydraulic cylinder 17 (FIGS. 1, 3) with a movably-installed body 18 (FIG. 3) and a fixed rod 19. The hydraulic cylinder 17 will be referred to hereinafter as braking cylinder.

The body 18 of the braking hydraulic cylinder 17 has an integral rack 20 which meshes with a toothed quadrant 21 secured on the bushed portion 10 of the bending head 8. The braking cylinder 17 retards the turning of the bending head while the pipe is being bent which ensures upsetting of the latter.

The hydraulic cylinder 17 communicates with the hydraulic cylinders 3 intended for longitudinal movement of the pipe. Such an arrangement is extremely diserable but not obligatory since the fluid can be drained in a usual way through a flow restrictor.

Interlocked with the body of the braking hydraulic cylinder 17 is an auxiliary hydraulic cylinder 22 (FIGS. 1, 3) which also rests on the slide 14. The body 23 (FIG. 3) of the hydraulic cylinder 22 is rigidly connected with the body 18 of the braking hydraulic cylinder I7 and, as a consequence, can move jointly with the latter. The rod 24 of the hydraulic cylinder 22 is an immovable element.

The hydraulic cylinder 22 communicates with a controllable source of pressure which is constituted by a variable-capacity hydraulic pump 25.

Installed on the bed 1 near the bending head 8 is a heater 26, for example a H.F. inductor though our invention is not confined to the use of any particular type of heater. The heater is intended to heat the pipe zone to be bent.

The hydraulic cylinders 3 and 17 are supplied from a hydraulic pump 27. Both hydraulic pumps 27 and 25 are powered by a common electric motor 28.

Before the beginning of the bending process the cantilever portion 9 of the bending head 8 is turned by the hydraulic cylinder 17 to a position coaxial with the bed 1 and is set for the desired bending radius. For this purpose the slide I4 is shifted by the drive 16 along the slot arranged across the bed 1 to the required distance from the longitudinal axis of the bed 1. The stop 4 is withdrawn to the rearrnost position on the rods 5. Then the pipe 12 to be bent is placed by a lifting crane on the rollers 2 of the bed and into the open bending head 8 so as to bring the front end of the pipe in contact with the stop 11 of the bending head.

The front end of the pipe is clamped in the bending head 8, its rear end is clamped in the supporting-andaligning rollers 29, the stop 4 is brought in contact with the rear end of the pipe and fixed in this position. Then the pipe zone to be bent is heated by switching on the heater 26.

On expiration of the time required for heating the bending zone to the preset temperature which depends on the thermoplastic properties of the pipe metal, the hydraulic pumps 27 and 25 are set in operation by switching on their drive motor 28. As a result, the working fluid begins to be fed simultaneously from the hydraulic pump 27 into the hydraulic cylinders 3 for longitudinal feed of the pipe and from the hydraulic pump 29 into the hydraulic control cylinder 22. The capacity of the hydraulic pump is selected to suit the parameters of the pipe being bent, the bending conditions, and the required degree of pipe upsetting.

This supply of the working fluid into the hydraulic cylinders 3 and 22 brings about the longitudinal feed of the pipe 12 towards the bending head and simultaneous turning of the bending head 8 with the predetermined braking. The working fluid forced out of the hydraulic cylinder 17 enters the working spaces of the hydraulic cylinders 3. Owing to the hydraulic communication between the hydraulic cylinders 3, 17 and 22, the ratio of the rate of longitudinal pipe feed to the turning speed of the bending head is retained at any given moment of time.

Thus, when the rate of longitudinal pipe feed is reduced due to an increased resistance of the pipe walls to the axial compression by the stop 4, the turning speed of the bending head is correspondingly decreased; conversely, when the rate of longitudinal pipe feed increases owing to a reduced resistance of the pipe walls to axial compression, the turning speed of the bending head will increase.

This eliminates the nonuniformity of axial compression of the pipe being bent and, consequently, the formation of wrinkles and variations in the thickness and strength of the pipe walls in the bending zone.

On completion of the bending process which is determined by the turning of the bending head through a preset angle corresponding to the preset pipe bending angle, the heater and the electric motor 28 are switched off and the hydraulic pumps and 27 are stopped.

The bending head releases the pipe 12, the stops 4 and 11 are again withdrawn to the extreme positions for releasing completely the pipe 12; then the pipe is clamped by grips in the crosspiece 6 which is connected with the rods 7 of the hydraulic cylinders 3 and the stepped rods 5. The no-load stroke of the hydraulic cylinders 3 sends the pipe 12 forward to the grips of the mechanism (not shown in the drawing) which removes the pipe from the bed 1. This mechanism may be constituted by any known device, e.g., a floor-mounted manipulator.

We claim:

1. A device for bending pipes comprising a bed in which the pipe to be bent is set with a provision for longitudinal movement; power cylinders for moving the pipe longitudinally on the bed; a bending head mounted on the bed rotatably in the bending plane; another power cylinder whose movable portion is connected with the bending head and which builds up a braking moment while said head is turned in the course of bending; one more power cylinder whose body is rigidly connected with the body of the braking power cylinder which is linked by its movable body with the bending head; a controllable source of pressure communicating with the power cylinder which is connected to the braking power cylinder.

2. A device according to claim 1 wherein the body of the braking power cylinder is connected with the body of the bending head by a gear-and-rack transmission.

3. A device according to claim 1 wherein the braking power cylinder communicates with the working spaces of the power cylinders provided for longitudinal movement of the pipe. 

1. A device for bending pipes comprising a bed in which the pipe to be bent is set with a provision for longitudinal movement; power cylinders for moving the pipe longitudinally on the bed; a bending head mounted on the bed rotatably in the bending plane; another power cylinder whose movable portion is connected with the bending head and which builds up a braking moment while said head is turned in the course of bending; one more power cylinder whose body is rigidly connected with the body of the braking power cylinder which is linked by its movable body with the bending head; a controllable source of pressure communicating with the power cylinder which is connected to the braking power cylinder.
 2. A device according to claim 1 wherein the body of the braking power cylinder is connected with the body of the bending head by a gear-and-rack transmission.
 3. A device according to claim 1 wherein the braking power cylinder communicates with the working spaces of the power cylinders provided for longitudinal movement of the pipe. 